Grade 7 Science

Grade 7 Science · State Standards

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Atoms, Elements, and Compounds

Atoms are building blocks of matter. An element contains one type of atom. A compound contains atoms of different elements chemically combined in a particular arrangement.

Example

A water molecule contains hydrogen and oxygen atoms. A mixture of different substances is not automatically a new compound.

Try it

Explain how a model of a compound would differ from a model of a mixture.

Evidence of Chemical Reactions

A chemical reaction rearranges atoms into new substances. New properties provide evidence of the change. An observation such as bubbling should be considered with the rest of the evidence.

Example

A gas may form when two materials react, but bubbles can also appear during boiling. The same observation can have different causes.

Try it

List observations that could support a reaction claim. Explain why one observation may not be enough.

Energy Transfer and Transformation

Energy can be transferred between objects and transformed among forms. A system model helps track where the energy goes. Energy that spreads to the surroundings still belongs in the account.

Example

A moving bicycle slows when braking. Some energy transfers to the brakes and surrounding air through heating.

Try it

Draw an energy-flow model for a braking bicycle. Include the surroundings.

Waves and Information

Waves can transfer energy and carry signals. Frequency and amplitude describe different features. A communication system needs a way to encode, transmit, and interpret information.

Example

A digital signal represents information using agreed symbols. A receiver uses the same code to interpret the message.

Try it

Design a simple code and explain how a receiver would distinguish its signals.

Photosynthesis and Food

In photosynthesis, organisms use light energy to make food from carbon dioxide and water. The process stores energy in food molecules. Plants also carry out cellular respiration.

Example

A leaf takes in carbon dioxide from air. Light supports the formation of sugars used by the plant and organisms that consume it.

Try it

Draw a photosynthesis model. Label inputs, outputs, and the energy source.

Cellular Respiration

Cells release usable energy from food through cellular respiration. In a common oxygen-using pathway, food and oxygen are involved and carbon dioxide and water are produced. Matter and energy have different roles in the model.

Example

A body cell uses materials supplied by digestive and respiratory systems. Its activity depends on those interacting systems.

Try it

Compare photosynthesis and respiration models. Identify a material that connects the processes.

Food Webs and Population Changes

Food webs show connections among organisms. A population change can have direct and indirect effects. Predictions should consider resources, competition, and more than one possible pathway.

Example

If a predator population declines, a prey population may increase, but limited food can affect how much it grows.

Try it

Predict two possible effects of a predator decline. State an assumption for each prediction.

Inheritance and Reproduction

Genetic information influences inherited traits. Different forms of reproduction produce different patterns of similarity and variation. Environmental conditions can affect how traits develop.

Example

Sexual reproduction combines genetic information from two parents. Offspring can resemble their parents without being identical to either one.

Try it

Explain why family resemblance does not mean all offspring have identical traits.

Natural Selection in a Population

Natural selection acts on existing variation in a population. In a particular environment, some inherited traits can contribute to survival and reproduction. Population patterns can change over generations.

Example

In an environment where camouflage affects survival, individuals with less visible coloring may leave more offspring. The population can change over time.

Try it

Describe a trait, an environmental condition, and a possible change over several generations.

Plate Motion and Earth’s Surface

Earth’s outer layer is divided into moving plates. Patterns in earthquakes, volcanoes, and rock evidence help scientists model plate motion. Different boundaries produce different effects.

Example

Many earthquakes occur along plate boundaries. Their locations provide evidence when compared with a plate map.

Try it

Explain how an earthquake map could support a model of plate boundaries.

Weather, Climate, and Energy

Weather is short-term atmospheric change; climate describes longer patterns. Unequal heating and movement of air and water influence those patterns. Explain a trend using a relevant range of data.

Example

An ocean can influence temperatures along a nearby coast. Air and water circulation help move energy among regions.

Try it

Explain why one unusual week does not establish a long-term climate trend.

Evaluating Evidence and Improving Models

A scientific model represents selected features of a system. Compare its predictions with observations. When evidence does not fit, consider the model’s assumptions and possible revisions.

Example

A food-web model that leaves out a competing species may predict a population change poorly. Adding a relevant connection can improve it.

Try it

Choose a model from a lesson. Describe one limitation and evidence that could help improve it.